Aqueous synthetic resin dispersion for the production of nontacky and nonblocking films and coatings



Patented Apr. 28, 1953 AQUEOUS SYNTHETIC RESIN DISPERSION FOR THEPRODUCTION AND NONBLOCKING FILMS AND INGS OF NONTACKY COAT- Harry E.Connors, Fairview Park, Ohio, and Arch L. Hatfield, Park Forest, 111.,assignors to The B. F. Goodrich Company, New York, N. Y., a corporationof New York No Drawing. Application March 31, 1951, Serial No. 218,706

Claims.

This invention relates to the production of aqueous dispersions ofsynthetic resins useful in forming non-tacky and non-blocking films andcoatings. The invention pertains more particularly to the production,from monomeric vinylidene chloride, vinyl chloride, alkyl acrylates suchas ethyl acrylate, and alkyl alkacrylates such as methyl methacrylate,of aqueous polymeric dispersions having new and unique properties,especially in regard to their ability to form films and coatings byair-drying at moderate temperatures, which films and coatings areplastic in nature yet are impermeable to moisture, greases and oils, andare not tacky at ordinary temperatures and do not block at elevatedtemperatures.

Two component or dual-copolymers of vinyl and vinylidene chloride witheach other or of either of these with an alkyl acrylate or methacrylateare all well known materials. While such copolymers are inherently morethermoplastic than polyvinyl or polyvinylidene chloride, they ordinarilyrequire the addition of plasticizers in order to form films and sheetsthereof and to render them sufiiciently flexible and plastic to beeasily subjected, at moderately elevated temperatures, to processingoperations such as molding, calendering, extruding and the like.Moreover, such copolymers, even when plasticized and cast from anaqueous dispersion or a solution in a volatile organic solvent in theform of films and coatings, require a heat treatment at elevatedtemperatures to effect a fluxing of the plasticized resin particles intoa continuous film. In addition, when such plasticized copolymers arecast in the form of films and coatings and heat-treated or fiuxed, thefinal cooled film or coating remains in a tacky condition so thatsticking occurs when other materials are placed in contact therewith orwhen a plurality of films or coatings are placed in contact one with theother. Such film and coatings are also somewhat permeable to water andare attacked by various fats and greases so that they are less valuablefor some uses, such as food packaging, than is desired.

In the copending application of Edward B. Osborne, Serial No. 772,002,filed August 27, 1947, there is disclosed a tripolymer latex made bypolymerization in aqueous emulsion of a monomeric mixture consisting offrom '75 to 90% by Weight of vinylidene chloride, 5 to by weight ofvinyl chloride, and from 5 to 15% by weight of an alkyl acrylate. Thislatex is useful without the addition of plasticizers for forming oft andplastic films and coatings by air-drying at temperatures from roomtemperature up to 50 C. The films and coatings thus produced, whilequite satisfactory for some purposes, have been found to possessproperties which seriously limit their use in certain otherapplications. For example, a film or coating deposited from the latex isoften tacky at ordinary temperatures so that foreign matter sticks tothe coating, or, even though the film or coating may not be tacky to thetouch at normal temperatures, it may become quite tacky when heated totemperatures of from to 150 F. The latter property, known as blocking,is especially undesirable in paper coating applications where the coatedpaper products of necessity have to be nested one within the other orotherwise placed in contact during shipment and distribution. A stillfurther often undesirable property of certain of the vinylidenechloride, vinyl chloride, alkyl acrylate tripolymers, especially thosecontaining from to by weight of vinylidene chloride (which are the leasttacky in nature), is their tendency to become crystalline and stiff uponaging.

Accordingly, it is one of the principal objects of this invention toprovide aqueous dispersions of polymeric materials containing no addedplasticizer which are superior to those of the abovementionedtripolymers in that they form films and coatings which are non-tacky atordinary temperatures and non-blocking at elevated temperatures. Anotherobject is the provision of an aqueous dispersion of thermoplasticpolymeric material useful in coating and packaging which possessesoutstanding impermeability to water and improved resistance to oils andgreases and the like. Still other objects are to provide a stablesynthetic resin latex which is useful for the production by air-dryingat moderate temperatures of films and coatings which are strong,flexible, and tack-free. Still other objects will be apparent from thedescription of the invention which follows.

We have found that aqueous synthetic resin dispersions, highly useful informing non-tacky and non-blocking films and coatings, are produced byincorporating an interpolymerized alkyl ester of an alpha-alkyl acrylicacid, such as methyl methacrylate, in an aqueous dispersion of aninterpolymer (hereinafter referred to as the basic tripolymer latex)resulting from the polymerization in aqueous emulsion of a monomericmixture comprising from 75 to 90% by weight of vinylidene chloride, toby weight of vinyl chloride, and from 5 to 15% by weight of an .alkylacrylate. The incorporation in the basic tripolymer latex of theinterpolymerized alkyl alkacrylate may be accomplished in several waysprovided that the finished latex contains as the dispersed phase aninterpoly-mer, or mixture of interpolymers, in which the relativeproportions of interpolymerized vinylidene chloride, vinyl chloride andalkyl acrylate remain the same as in the basic tripolymer latex and theproportion of interpolymerized alkyl alkacrylate i from 0.5 to 7.5 byweight based on the weight of the basic tripolymer.

One convenient method of incorporating interpolymerized alkylalkacrylate consists in add ing an aqueous disperson of a vinylidenechloride alkyl alkacrylate interpolymer (hereinafter referred to as theblending latex) made by polymerizing in aqueous emulsion a monomericmixture containing at least two essential ingredients, one being from 85to 95% by weight of vinylidene chloride and the other from 5 to 15% byweight of an alkyl alkacrylate. In addition to the two essentialmonomers utilized in the production of the blending latex, minorproportions of vinyl chloride may be substituted for up to one-half ofthe alkyl alkacrylate so as to produce a threecomponent interpolymer ortripolymer blending latex, in which case the monomeric mixture willconsist of from 85 to 95% by weight of vinylidene chloride, 2 to 7.5% byweight of vinyl chloride and from 2 to 7.5% by weight of alkylalkacrylate. The utilization of such a tripolymer blending latex isgreatly preferred since the resulting aqueous dispersion produces filmsand coatings having lower fusion temperatures, greater softness .andpliability combined with good blocking characteristics. When atwo-component interpolymer or copolymer blending latex is utilized theproportions of latices blended, on the dry solids basis, shouldpreferably be between the Weight ratios .of 2:1 and 1 :2 of the basictripolymer latex and blending copolymer latex, respectively. The use ofa tripolymer blending latex permits slightly greater latitude in theproportions of each latex utilized, the blending ratio in this casepreferably varying from 3:1 to 1:3.

Another method of incorporating the interpolymerized alkyl alkacrylateis to interpolymerize the latterwith the monomeric vinylidene chloride,vinyl chloride and alkyl acrylate in the preparation of the basictripolymer latex. In the latter case a true tetrapolymer latex isbelieved to result from the interpolymerization in aqueous emulsion of amonomeric mixture consisting of from 75 to 89% by weight of vinylidenechloride, from 5 to 15% by weight of vinyl chloride, from 5 to 10% ofalkyl acrylate and from 1.0 to 7.5% by weight of alkyl alkacrylate. Anyof these methods result in aqueous polymeric dispersions from whichfilms and coatings may be produced which are soft and flexible and yetare non-tacky and non-blocking in nature and do not become crystallineand stiif upon aging.

Any of the alkyl esters of acrylic acid may be employed in thepreparation of the basic tripolymer latex. For example, methyl acrylate,ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-

butyl acrylate, isobutyl acrylate, n-amyl acrylate, Z-ethylhexylacrylate, 3,5,5-trimethylhexyl acrylate, n-decyl acrylate, laurylacrylate, n-octadecyl acrylate, and others may be used. It is preferred,however, to employ those alkyl acrylates which contain less than eightcarbon atoms in the molecule. Methyl and ethyl acrylate produce the bestinterpolyniers for the purposes of this invention.

Any of the alkyl esters of alpha-alkyl acrylic acids may also beemployed for producing interpolymerized alkyl alkacrylate to beincorporated with the basic latex. Thus, such alkyl alkacrylates asmethyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butylmcthacrylatc, methyl ethacrylate, ethyl ethacrylate and others may beused. Methyl methacrylate because of its ready availability, low costand its ability to form interpolymers or" greatly superior blockingproperties is the alkyl alkacrylate to be greatly preferred.

In the practice of this invention particularly valuable basic tripolymerfilm-forming latices are those prepared from monomeric mixturesconsisting of vinylidene chloride, vinyl chloride and ethyl acrylate inthe ratios by weight: 77:11.5:11.5, 80:10:10 and :5:10. Particularlyvaluable as blending latices are the latices resulting from monomericmixtures consisting of vinylidene chloride, vinyl chloride and methylmcthacrylate in the ratios: :5:5 and. 88:7:5 and the latex resultingfrom a monomer mixture consisting of vinylidene chloride and methylmethacrylate in the ratio of 90:10.

The aqueous dispersions of polymeric latices utilized in preparing thefilm-forming aqueous dispersion of this invention may be prepared by anyof the conventional emulsion polymerization techniques employing anefficient emulsifying agent to obtain a stable final product. There maybe used as an emulsifier the ordinary soaps such as the alkali metal,ammonium and alkanol amine salts of fatty acids including sodium oleate,potassium palmitate, ammonium stearate, ethanol amine laurate, and thelike as well as rosin and. dehydrogenated rosin acid soaps, and thesynthetic saponaceous materials including the hymolal sulfates andsulfonates such as sodium lauryl sulfate, sodium cetyl sulfate, thesodium salts of sulfonated paraffin oils, the sodium salts ofdodecane-l-sulfom'c acid, octadecane-l-sulionic acid, etc., the alkarylsulfonates such as the sodium alkyl aryl sulfonates such as sodiumisopropyl benzene sulfonate, sodium isopropyl naphthalene sulfonate, thealkali metal salts of sulfonated dicarboxylic acid esters and amidessuch as sodium dioctyl sulfosuccinate, sodium N-octadecyl-sulfonsuccinamate, and the like and salts of organic basescontaining long carbon chains such as the hydrochloride ofdiethylaminoethyloleylamide, lauryl amine hydrochloride, trimethyl cetylammonium bromide, and the like.

While the polymerization reaction to form any of the polymeric laticesfor use in this invention may be carried out in the presence of air, therate of reaction is ordinarily faster in the absence of gaseous oxygenand hence polymerization in an atmosphere of monomer or inert gas ispreferred. The temperature at which the polymerization is carried out isnot critical, it may be Varied Widely from 0 C. up to C. or higher,though best results are generally obtained at a temperature from about20 to 70 0.

Any of the catalysts commonly employed for the polymerization of vinyland vinylidene compounds may be used in preparing the polymeric latices.Actinic radiation may be employed, as well as the various peroxygencompounds such as hydrogen peroxide, potassium persulfate, benzoylperoxide, o,o-dichlorobenzoyl peroxide, caprylyl peroxide, sodiumperborate, sodium percarbonate, and the like. A preferred catalyst foruse in this invention is potassium persulfate. Buffers such as sodiumcarbonate, disodium phosphate, ammonium hydroxide, and others may beutilized to maintain the desired pH during the reaction.

The following specific examples describe the invention in greaterdetail, particularly with regard to the preparation of specificpreferred polymer latices, their blending and the properties of filmsand coatings which are prepared therefrom. The examples are intendedmerely as illustrations of the nature of our invention and not aslimitations on the scope thereof.

Example 1 A tripolymer latex was produced by the polymerization at 50 C.of the monomeric materials contained in a reaction mixture containingthe following ingredients.

Material: Parts/wt. Vinylidene chloride 77.00 Vinyl chloride 11.50 Ethylacrylate 11.50 Emulsifier 1 3.00 Disodium phosphate 0.70 Trisodiumphosphate 0.30 Potassium persulfate 0.70 Latex seed 8.00

Water, soft 95.00

1 A sulfonated paraffin oil known as Duponol MP 1893. The product is astable polymer latex of approximately 50% total solids content.

A second tripolymer latex is prepared by the polymerization at 50 C. ofthe monomeric materials contained in a reaction mixture having thefollowing composition.

Material: 5 Parts wt. Vinylidene chloride 90.0 Vinyl chloride 5.0 Methylmethacrylate 5.0 Emulsifier 1 3.0 Disodium phosphate 0.6 Potassiumpersulfate 0.6 Latex seed 4.0 Water 95.0

1 Same as above.

The product likewise is a stable polymeric latex containing about 50%total solids.

The two tripolymer latices are blended in 50:50 proportions simply bystirring the two together. The blended dispersion is as stable as eitherof the component latices and needs only the addition of about 1% ofcarboxymethyl or hydroxyethyl cellulose, polyacrylic acid orpolyacrylamide thickening agents to be suitable for film casting orcoating applications. A film 4 mils in thickness deposited from theblended latex and dried at room temperature C.) has a tensile strengthof 2700 lbs/sq. in., an elongation of 110%, and a Graves tear strengthof 600 lbs/in. The film when fused at 225 F. has a tensile strength of3200 lbs/sq. in., an elongation of 110% and a Graves tear strength of750 lbs/in. A sheet of 50 lb. super calendered kraft paper coated withpolymer from the latex blend to a thicknessof 1 mil has a moisture vaportransmission (M. V. T.) of only 0.6 gin/100 sq.

ill/241101115 and, in addition, has very good grease resistance. Thecoating is clear and glossy, is tightly adherent to the paper base, isvery dry to the touch, does not stiffen upon aging at 100 F. for as muchas 3 months, and has unusually good blocking characteristics as shown bya test in which a weight of 1 lb./sq. in. is placed on top of two sheetsof film in face-toface relationship and heated at a temperature of 120F. for 16 hours. Under this test the two sheets of film in each casefell apart of their own weight when the weight was removed. Sim-- ilarfilms formed from the unblended basic polymer latex are so tightlyadherent when subjected to this test as to require the exertion ofconsiderable force in order to be separated. Paper and boxboard coatedwith the blended latex are ideal packaging materials because they arefiexible, resistant to the transmission of moisture vapor and grease,are not tacky to the touch, do not stick to like-coated surfaces, andmay be heat-sealed when one coated surface is in contact with another.Cap liners, soap cartons, frozen food cartons and wrappers, and icecream and milk cartons are but a few of the types of food packages whichcan be made from unsupported films or coated papers prepared from theblended latex of this example.

Similar results are obtained by blending from as much as by weight ofthe basic tripolymer latex and 25% of the blending latex to as little as25% of the basic latex and 75% of the blending latex. A tripolymer latexmade from monomeric mixtures consisting of vinylidene chloride, 10%vinyl chloride and 10% ethyl acrylate blended with similar proportionsof a latex resulting from a monomeric mixture of vinylidene chloride,7.5% vinyl chloride and 7.5% methyl methacrylate produces a blendedaqueous dispersion useful in the production of flexible but tough,non-tacky and non-blocking films and coatings.

Example 2 A copolymer latex is prepared by polymerizing at 50 C. themonomeric materials contained in a reaction mixture having the followingcomposition.

Material: Parts/wt. Vinylidene chloride 90.0 Methyl methacrylate 10.0Disodium phosphate 0.6 Potassium persulfate 0.6

Emulsifier 3.0

Latex seed 6.0

Water 95.0

1 Same as in Example 1.

The product is a stable white latex containing about 50% total solids.

The copolymer latex is blended with a 77:11.5: 11.5 vinylidene chloride,vinyl chloride and ethyl acrylate latex similar to that of Example 1 inthe weight ratio of 1:2. The resulting latex blend thickened with 1% byweight based on the latex solids basis of carboxymethyl cellulose isused to cast a a mil unsupported film and a 1 mil coating on paperboxboard each being dried at 50 C. in air. The resulting film andcoating is smooth, glossy and dry to the touch at ordinary temperatures,has good blocking characteristics, and does not stiffen appreciably inservice. The filmand coating are slightly harder and less thermoplasticthan those of Example 1.

Example 3 A stable polymeric dispersion is obtained by polymerizing at50 C. the monomeric materials contained in a reaction mixture having thefollowing composition.

Material: Parts/wt. Vinylidene chloride 77.0 Vinyl chloride 11.5 Ethylacrylate 7.0 Methyl methacrylate 4.5 Potassium persulfate 0.6 Disodiumphosphate 0.6 Emulsifier 1 3.0 Latex seed 4.0 Water 95.0

1 Same as in previous examples.

At the end of 16 hours the reaction is substantially complete with theproduction of a stable white latex containing over 50% total solids.

The resulting tetrapolymer latex is thickened by the addition of about0.2 part of hydroxymethyl cellulose per 100 parts by weight of latexsolids and cast on glass plates so as to form a dried film about 4 milsin thickness. The film is dried at 35 C. and then stripped from theglass plates and found to be soft, flexible and transparent. The film isfound to have a tensile strength of 3,000 lbs/sq. in. and an elongationat break of 200%. After aging for 20 days at 70 C. the film is found tobe soft and flexible and to have a tensile strength of 4100 lbs/sq. in.and an elongation of 225%. A sample of film similarly prepared from thelatex of this example by air-drying at 50 C. has an initial tensilestrength of 3700 lbs/sq. in. and an elongation of 200%. Thus thetetrapolymer latex has the property of forming excellent strong films byair-drying at moderate temperatures. Such films can not be formed fromvinylidene chloride vinyl chloride copolymer latices, or from vinylidenechloride ethyl acrylate latices, or from vinylidene chloride methylmethacrylate copolymer latices, even when substantial mounts of liquidplasticizers are added.

The latex of Example 3 has other desirable properties including an M. V.T. of 0.6 gin/100 sq. in. in 24 hours, excellent grease resistance attemperatures as low as -l0 F., and excellent blocking characteristics sothat at temperatures as high as 120 F. no sticking together of films orcoated boxboard sheets is observed, The properties of the tetrapolymerlatex make it ideal for use in the paper-coating industry whereresincoated packaging materials are frequently stored or shipped in theknocked-down condition.

Similar results are obtained from latices'made by polymerizing inaqueous emulsion of monomeric mixtures containing, respectively, 78.5%vinylidene chloride, 10% by weight of vinyl chloride, 7.0% of ethylacrylate, and 4.5% methyl methacrylate; 77% vinylidene chloride, 12%vinyl chloride, 6.5% methyl acrylate, and i.5% methyl methacrylate; and85% vinylidene chloride, vinyl chloride, 7.5% ethyl acrylate, and 2.5%ethyl ethacrylate.

Other polymeric dispersions similar to those described in Examples 1 to3 are obtained with other alkyl esters of acrylic acid and with otheralkyl esters of alkacrylic acids. Other polymerization conditions,catalysts, emulsifiers and the like are utilizablc with equivalentresults. Plasticizers, stabilizers, fillers, coloring pigments,lubricants and other substances may be incorporated in the aqueousdispersion, if desired, in the manner well understood in the art.

While we have disclosed with considerable detail certain preferredmanners of performing the invention, it is not intended or desired to belimited solely thereto, for as hitherto stated, the procedure may bemodified, the precise proportions of the materials utilized may bevaried, and other materials having equivalent properties may beemployed, if desired, without departing from the spirit and scope of theinvention as defined in the appended claims.

We claim:

1. An aqueous dispersion of synthetic resin useful in forming non-tackyand non-blocking films and coatings under moderate fusion temperatures,said dispersion containing as the disperse phase a mixture of polymericmaterials comprising (1) a tripolymer resulting from the polymerizationin aqueous emulsion of a mixture of monomeric materials consisting offrom 75 to 90% by weight of vinylidene chloride, from 5 to 15% by weightof vinyl chloride, and from 5 to 15% by weight of an alkyl acrylate and(2) a vinylidene chloride alkyl alkacrylate interpolymer selected fromthe class consisting of (a) a two-component interpolymer made bypolymerizing in aqueous emulsion a monomeric mixture consisting of fromto 95% vinylidene chloride and from 5 to 15% by weight of an alkylallzacrylate and (b) a threecornponent interpolymer made by polymeriznigaqueous emulsion a monomeric mixture consisting of 85 to 95% vinylidenechloride, 2 to 7.5% by weight of vinyl chloride and 2 to 7.5% by weightof an alkyl alkacrylate, the said mixture of polymeric materialscontaining from 33 to 552 70 by weight of tripolymer 1) and from 33% to56 by weight of interpolymer (2) when said interpolymer is saidtwo-component interpolymer (a), and from 25 to 75% by weight oftripoiyrner (1) and from 25 to 75% by weight of interpolymer (2), whensaid intcrpolymer is said three-component interpolymer (1)).

2.1111 aqueous dispersion of synthetic resin useful in forming non-tackyand non-blocking films and coatings under moderate fusion temperat-ures,said dispersion containing as the disperse phase a mixture of polymericsubstances comprising (1) a tripolymer resulting from the polymerizationin aqueous emulsion a mixture of monomeric materials consisting of from'75 to by weight of vinylidene chloride, from 5 to 15% by weight ofvinyl chloride and from 5 to 15% by weight of an alkyl acrylate and (2)a tripolyrner resulting from the polymerization of a monomeric mixtureconsisting of from 85 to by weight or vinylidene chloride, from 2 to7.5% by weight of vinyl chloride, and from 2 to 7.5% by weight of methylmethacrylate, the said mixture of polymeric substances containing from25 to 75% by weight of tripolymer 1) and from 25 to 75% by weight oftripolymer ('2).

3. An aqueous dispersion of synthetic resin useful in forming non-tackyand non-blocking films and coatings under moderate fusion temperatures,said dispersion containing as the disperse phase a mixture of polymericsubstances comprising (1) a tripolymer resulting from the polymerizationin aqueous emulsion a mixture of monomeric materials consisting of from75 to 90% by weight of vinylidene chloride, from 5 to 15% by weight ofvinyl chloride, and from 5 to 15% by weight of an alkyl acrylate and (2)a copolymer resulting from the polymerization in aqueous emulsion of amonomeric mixture consisting of from 85 to 95% by weight of vinylidenechloride and from to 15% by weight of methyl methacrylate, said mixtureof polymeric substances containing from 33 to 66 /3% by weight oftripolymer (l) and from 33 to 66 /39}, by weight of copolymer (2) 4. Anaqueous dispersion of synthetic resin useful in forming non-tacky andnon-blocking films and coatings under moderate fusion temperatures, saiddispersion containing as the disperse phase a mixture of polymericsubstances comprising (1) a tripolymer resulting from the polymerizationin aqueous emulsion of a monomeric mixture comprising from '75 to 90% byweight of vinylidene chloride, from 5 to 15% by weight of vinylchloride, and from 5 to 15% by weight of ethyl acrylate and (2) atripolymer resulting from the polymerization of a monomeric mixtureconsisting of from 85 to 95% by Weight of vinylidene chloride, from 2 to7.5% by weight of vinyl chloride, and from 2 to 7.5% by weight of methylmethacrylate, said mixture of polymeric substances containing from 25 to75% by Weight of tripolymer (1) and from 25 to 75% by weight oftripolymer (2).

5. .An aqueous dispersion of synthetic resin useful in forming non-tackyand non-blocking films and coatings under moderate fusion tem peratures,said dispersion containing as the disperse phase a mixture of polymericsubstances comprising (1) a tripolymer resulting from the polymerizationin aqueous emulsion a mixture of monomeric materials consisting of fromto by weight'of vinylidene chloride, from 5 to 15% by weight of vinylchloride, and from 5 to 15% by weight of ethyl acrylate and (2) acopolymer resulting from the polymerization in aqueous emulsion of amonomeric mixture con-- sisting of from S5 to by weight of vinylidenechloride and from 5 to 15% by weight of methyl methacrylate, saidmixture of polymeric materials containing from 33 /3 to 66 by weight oftripolymer (1) and from 33 to 66 75 by weight of copolymer (2).

HARRY E. CONNORS.

ARCH L. HATFIELD.

References Cited in the file of this patent FOREIGN PATENTS NumberCountry Date 605,517 Great Britain July 26, 1948

1. AN AQUEOUS DISPERSION OF SYNTHETIC RESIN USEFUL IN FORMING NON-TACKYAND NON-BLOCKING FILMS AND COATINGS UNDER MODERATE FUSION TEMPERATURES,SAID DISPERSION CONTAINING AS THE DISPERSE PHASE A MIXTURE OF POLYMERICMATERIALS COMPRISING (1) A TRIPOLYMER RESULTING FROM THE POLYMERIZATIONIN AQUEOUS EMULSION OF A MIXTURE OF MONOMERIC MATERIALS CONSISTING OFFROM 75 TO 90% BY WEIGHT OF VINYLIDENE CHLORIDE, FROM 5 TO 15% BY WEIGHTOF VINYL CHLORIDE, AND FROM 5 TO 15% BY WEIGHT OF AN ALKYL ACRYLATE AND(2) A VINYLIDENE CHLORIDE ALKYL ALKACRYLATE INTERPOLYMER SELECTED FROMTHE CLASS CONSISTING OF (A) A TWO-COMPONENT INTERPOLYMER MADE BYPOLYMERIZING IN AQUEOUS EMULSION A MONOMERIC MIXTURE CONSISTING OF FROM85 TO 95% VINYLIDENE CHLORIDE AND FROM 5 TO 15% BY WEIGHT OF AN ALKYLALKACRYLATE AND (B) A THREECOMPONENT INTERPOLYMER MADE BY POLYMERIZINGIN AQUEOUS EMULSION A MONOMERIC MIXTURE CONSISTING OF 85 TO 95%VINYLIDENE CHLORIDE, 2 TO 7.5% BY WEIGHT OF VINYL CHLORIDE AND 2 TO 7.5%BY WEIGHT OF AN ALKYL ALKACRYLATE, THE SAID MIXTURE OF POLYMERICMATERIALS CONTAINING FROM 331/3 TO 66 2/3 BY WEIGHT OF TRIPOLYMER (1)AND FROM 331/3 TO TO 66 2/3% BY WEIGHT OF INTROPOLYMER (2), WHEN SAIDINTERPOLYMER IS SAID TWO-COMPONEN INTERPOLYMER (A), AND FROM 25 TO 75%BY WEIGHT OF TRIPOLYMER (1) AND FROM 25 TO 75% BY WEIGHT OF INTERPOLYMER(2), WHEN SAID INTERPOLYMER IS SAID THREE-COMPONENT INTERPOLYMER (B).